Semiconductor device and method for manufacturing the same

US8963155B2 · kind B2 · utility

Assignee

• Semiconductor Energy Laboratory Co., Ltd. · JP

Inventors

• Hajime Tokunaga · Yokohama, JP
• Takuya Handa · St Pierre, MU

Key dates

• Filing date: Jul 29, 2013
• Grant date: Feb 24, 2015
• Expiry date: Jul 29, 2033

Classification

• Technology area (CPC —): General

Abstract

To provide a semiconductor device which has transistor characteristics with little variation and includes an oxide semiconductor. The semiconductor device includes an insulating film over a conductive film and an oxide semiconductor film over the insulating film. The oxide semiconductor film includes a first oxide semiconductor layer, a second oxide semiconductor layer over the first oxide semiconductor layer, and a third oxide semiconductor layer over the second oxide semiconductor layer. The energy level of a bottom of a conduction band of the second oxide semiconductor layer is lower than those of the first and third oxide semiconductor layers. An end portion of the second oxide semiconductor layer is positioned on an inner side than an end portion of the first oxide semiconductor layer.